Catalog LV 70 2011 - Low & Medium Voltage - Siemens

© Siemens AG 2011
Appendix
Isolating function
(see also IEC/EN 60947-1; 2.1.19)
Mechanical shock resistance
Protection against accidental direct contact
(see also EN 50274; 3.4)
Positively-driven operation
(see also IEC/EN 60947-1; 2.4.11 / IEV 441-16-12)
Positive or
enforced operation/actuation
Positive opening
(see also IEC/EN 60947-1; 2.4.10 / IEV 441-16-11)
Safe isolation
(see also IEC/EN 61140; 3.24)
Tamper proof
Type of coordination
Utilization category
(see also IEC/EN 60947-1; 2.1.18/IEV 441-17-19)
(see also IEC/EN 60947-2; 4.4)
Glossary
Equipment is deemed to possess this isolating function provided their
switching contacts, when in the open position, achieve the separation
distance prescribed for the isolation of electrical circuits, and their
clearance and creepage distances are of the required size. The
power supply to the entire installation or a section of the installation can
thus be cut off for safety reasons, e.g. during maintenance.
The capacity of an equipment to withstand pulse-like motions without
changing its operating state or sustaining damage. No contact lifting
must take place on devices in the On position, the main contacts must
not knock against one another in the Off position. A protective switch
must not trip, and auxiliary switches must not change their switching
state.
Design measures incorporated into equipment in order to prevent
direct contact (i.e. without tools) with live parts of a system (finger-safe,
back-of-hand proof).
This ensures that the auxiliary contacts of a switching device are
always in the switch position corresponding to the open or closed position
of the main contacts. The contacts of contactors are positively
driven contacts, provided they are mechanically linked in such a way
as to ensure that normally closed contacts and normally open contacts
can never be closed simultaneously. This arrangement must also
ensure that minimum contact separation of 0.5 mm is maintained over
the entire endurance of the device, even during a fault (e.g. welding of
one contact). The pertinent German Trade Association requires the use
of contactors with positively driven contacts for control systems on
power presses in the metal processing industry.
This describes an arrangement where a link between the actuator and
the contact ensures that the force exerted on the actuator is transferred
directly (without the intervention of sprung parts) onto the contact.
An opening operation which ensures that the main contacts of a switching
device have attained the open position when the actuator is in the
Off position.
Isolation of circuits not carrying hazardous voltages, e.g. protective
extra-low voltage, from circuits in which hazardous voltages flow. Such
isolation is achieved by means of reinforced or double insulation, which
reliably prevents voltage transfer from one circuit to another. This might
otherwise take place between main circuits and auxiliary circuits in
switching devices or between primary and secondary in safety transformers.
Safe isolation is a priority requirement for safety circuits and
functional low-voltage circuits.
An EMERGENCY-STOP switching device is regarded as tamper
proof provided it cannot be reset without tools or via prescribed procedure,
after tripping has taken place. The device latches in the tripped
position. Accidental or deliberate manipulation (inching) is ruled out.
Status of a controlgear combination (motor starter) during and after
testing at rated conditional short-circuit current:
• Type of coordination 1:
- no risk to persons or installations
- no requirement for immediate readiness for renewed operation
- damage to the starter is admissible
• Type of coordination 2:
- no risk to persons or installations
- starter is capable of renewed operation
- no damage to the starter with the exception of a slight welding of the
switching contacts, provided they can be separated without significant
deformation
A combination of specified requirements relating to the operating condition
in which the switching device or fuse fulfills its purpose, selected
to represent a characteristic group of practical applications. The specified
requirements may concern, for example, the values of making
capacity, breaking capacity and other characteristic values, data concerning
associated circuits, and the relevant conditions of use and
operation characteristic.
For circuit breakers, the utilization category denotes whether the equipment
is designed for selectivity using time delay (category B) or not
(category A).
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